It is not uncommon for a wheeled vehicle to become immobilized in shifting or otherwise slippery surface. The prior art is includes examples of apparatus for providing mobility to the wheeled vehicle in these conditions. These prior art devices are typically either of a mat arrangement or a framed apparatus arrangement positioning between the drive train wheel of the vehicle and the shifting surface for fixing the vehicle relative to the surface.
U.S. Pat. Nos. 3,640,459; 3,749,309; 4,261,510 and 5,439,171 are typical examples of the mat arrangements found in prior art traction devices. Traction devices with a mat arrangement are predominately a flat or curved surface that is used to cover the shifting surface. In this way, the mat provides friction and traction between the wheel and the shifting surface.
Prior art traction mats are deficient in that the mat's predominately flat surface catches the build-up of loose material dislodged from the shifting surface and lodged in tracks of the wheel. Portions of the shifting surface on which the wheeled vehicle rested is deposited on the flat surface of the mat thereby creating a secondary shifting surface of the same composition. The wheel that was once immobilized on the shifting surface would then be immobilized on the secondary shifting surface formed between the wheel and the mat's flat surface.
Framed traction devices are typically composed of various frame shapes. For example, U.S. Pat. No. 6,129,289 features a traction device with a U-shaped frame. The U-shaped frame includes a plurality of traversing braces each having downwardly facing cleats to engage the shifting surface. U.S. Pat. No. 3,878,988 is another U-shaped frame traction device with traversing braces and downwardly facing cleats. The traversing braces of the device disclosed in the '988 patent are curved to fit into engagement with laterally traversing wheel tread cavities. U.S. Pat. No. 4,300,722 discloses another example of a framed traction device comprising a unitary elongated stamped metal structure that is generally rectangular but tapers forwardly and inwardly at one end. The upper surface of the device is flat and includes rectangular openings. The device upper surface includes upwardly extending gripping flanges while the lower surface includes V-shaped gripping lugs. U.S. Pat. No. 6,520,420 is another exemplary prior art frame traction device. The frame in this traction device is rectangular shaped and includes a plurality of traversing braces such that the openings created by the brace placement supplies rectangular openings.
The prior art framed traction devices are deficient in that their respective structures offer limited load bearing capacity, and proper useful traction surface,
What is needed is a traction device whose construction is minimilized for optimal load bearing and easy storage.